The inclusion of sensors in portable electronic devices has become increasingly popular. During a group activity, users of such devices can expect that individual specific sensor measurements such as heart rate will differ. However, during the same group activity, the users might expect that sensors generating user-invariant data such as distance travelled and elevation gained should produce consistent measurement results among different devices. The existence of extrinsic variables, i.e., variables that can affect measurement values but are not intended to be measured such as temperature and/or humidity, can cause two user devices engaged in the same activity to report different sensor measurement values (e.g., distance traveled). This type of discrepancy can cause users to question the validity and accuracy of sensor measurement data obtained by their devices.